1261. Find Elements in a Contaminated Binary Tree

Medium

Given a binary tree with the following rules:

1. root.val == 0

2. If treeNode.val == x and treeNode.left != null, then treeNode.left.val == 2 * x + 1

3. If treeNode.val == x and treeNode.right != null, then treeNode.right.val == 2 * x + 2

Now the binary tree is contaminated, which means all treeNode.val have been changed to -1.

Implement the FindElements class:

• FindElements(TreeNode* root) Initializes the object with a contaminated binary tree and recovers it.

• bool find(int target) Returns true if the target value exists in the recovered binary tree.

Example 1:

Input
["FindElements","find","find"]
[[[-1,null,-1]],[1],[2]]
Output
[null,false,true]
Explanation
FindElements findElements = new FindElements([-1,null,-1]); 
findElements.find(1); // return False 
findElements.find(2); // return True 

Example 2:

Input
["FindElements","find","find","find"]
[[[-1,-1,-1,-1,-1]],[1],[3],[5]]
Output
[null,true,true,false]
Explanation
FindElements findElements = new FindElements([-1,-1,-1,-1,-1]);
findElements.find(1); // return True
findElements.find(3); // return True
findElements.find(5); // return False

Example 3:

Input
["FindElements","find","find","find","find"]
[[[-1,null,-1,-1,null,-1]],[2],[3],[4],[5]]
Output
[null,true,false,false,true]
Explanation
FindElements findElements = new FindElements([-1,null,-1,-1,null,-1]);
findElements.find(2); // return True
findElements.find(3); // return False
findElements.find(4); // return False
findElements.find(5); // return True

Constraints:

• TreeNode.val == -1

• The height of the binary tree is less than or equal to 20

• The total number of nodes is between [1, 10^4]

• Total calls of find() is between [1, 10^4]

• 0 <= target <= 10^6

解題

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
type FindElements struct {
    tree *TreeNode
}


func Constructor(root *TreeNode) FindElements {
    root.Val = 0 
    createTree(root)
    return FindElements{ tree: root }
}

func createTree(root *TreeNode) {
    if root == nil { return }

    if root.Left != nil {
        root.Left.Val = 2 * root.Val + 1
    }

    if root.Right != nil {
        root.Right.Val = 2 * root.Val + 2
    }

    createTree(root.Left)
    createTree(root.Right)
}

func (this *FindElements) Find(target int) bool {
    return find(this.tree, target)
}

func find(root *TreeNode, target int) bool {
    if root == nil { return false }
    if root.Val == target { return true }

    return find(root.Left, target) || find(root.Right, target)
}


/**
 * Your FindElements object will be instantiated and called as such:
 * obj := Constructor(root);
 * param_1 := obj.Find(target);
 */